1. Field of the Invention
The present invention is broadly concerned with an improved process for the preparation of granular cold water swelling/soluble starches which provide instant thickening without lumpiness when hydrated in cold water. More particularly, it is concerned with a process wherein granules of starch are treated with alcohol and a strong base to cause swelling of the granules and conversion to a form having increased cold water solubility. The starch material thus prepared has an ability to set to a sliceable gel without cooking or chilling. Pastes prepared from granular cold water swelling/soluble starches at room temperature give a smooth texture with no lumps.
2. Description of the Prior Art
Starches which provide instant thickening are used to shorten or eliminate cooking time in convenience foods, such as soups, puddings and breading batters. In the conventional processes for making instant starches, a starch slurry is simultaneously cooked and dried on a drum dryer to give a thin sheet, which is subsequently ground to a fine powder. Such drum-cooked instant starches often give inferior performance in foods as compared with cook-up starches. This is believed to result from the fact that on the hot drum, the cooked granules fuse together and are strongly cemented to form a starch sheet. Fine grinding of the sheet gives irregularly shaped particles that contain retrograded starch, leading to a grainy appearance upon rehydration. In addition, drum-cooked instant starches have reduced consistency upon rehydration to a paste and form gels of reduced strength. Recently developed methods yield pre-gelatinized starches with granular integrity but are not universally successful for waxy, high-amylose, and normal starches. Some granular cold water-soluble starches hydrate in cold to warm solutions of sugar without lumping, and their pastes are on a par with cook-up starches. Others hydrate in cold water without lumping, but have reduced capacity to generate thickening power.
In addition, prior methods of producing instant starches are not generally applicable to all types of starches such as waxy, high amylose and normal starches. Accordingly, it has been necessary to vary the processing techniques for the various types of starches, in order to successfully produce instant starches.
U.S. Pat. No. 4,465,702 describes a process of thermal treatment of native corn starch in aqueous alcohol solutions. The starch thus treated remains in granular shape, but becomes cold water soluble.
U.S. Pat. No. 4,634,596 describes a thermal treatment of mixtures of waxy and normal starches in aqueous alcohol solutions; 20% to 70% of waxy starch was blended in the starch mixture. The mixed starches became cold water soluble, but retained the granular shape.
U.S. Pat. No. 3,399,081 describes the preparation of nonbirefringent granular starches which give pastes when mixed with cold water. The starch is prepared by treating native starch with a mixture of ammonia and methanol at low temperatures. The product has a swelling power of 17, soluble value of 36%, and a fat content of 0.4% at 25.degree. C.
U.S. Pat. No. 847,658 describes a process of preparing starch capable of swelling in cold water by first mixing the starch with a liquid hydrocarbon such as paraffin oil and then adding caustic alkali.
U.S. Pat. No. 4,229,489 describes a process of preparing cold water dispersible tapioca starch by cross-linking followed by acid thinning and drum-drying.
U.S. Pat. No. 4,260,642 describes a process of preparing instant starches for pudding mixes. A native or modified starch slurry is gelatinized in the presence of sodium or calcium stearyl-2-lactylate and then drum dried and ground.
U.S. Pat. No. 4,280,851 describes the use of multiple-port nozzles in a spray dryer to gelatinize and recover essentially intact granular cooked starch.